The characterization of genomic instability in Schizosaccharomyces pombe cdc24 mutants

As cells divide, it is crucial that they pass on precise copies of their genomes. Failure to replicate appropriately can result in genetic instability, where a genome becomes vulnerable to changes and mutations. Cdc24 is a protein implicated in lagging strand synthesis and DNA damage repair in Schizosaccharomyces pombe. Moreover, Cdc24 plays a role in genome stability. cdc24 mutants arrest in S-phase with broken chromosomes. In order to understand the chromosome breakage phenotype, we look at cdc24 mutants in the absence of Mus81, a conserved endonuclease implicated in DNA replication and DNA damage response. Spot assays and pulsed field gel electrophoresis were used to analyze cdc24 mutant cells with a Mus81 delete background. Additionally, a viability assay was used to determine whether the loss of viability in cdc24 mutant cells is due to chromosome breakage. Our investigation demonstrates that the chromosome breakage phenotype exhibited in cdc24 mutants is Mus81-dependent. We also conclude that the loss in viability that we observe in cdc24 mutants is not due to DNA fragmentation. Additionally, these data suggest that Cdc24 may play an important a role in stabilizing replication forks. Further analysis of genome instability in cdc24 mutants can contribute to a better understanding of genome instability in higher eukaryotes.